This invention relates to certain titanium and zirconium complexes comprising a single, cyclic, delocalized .pi.-bonded ligand group wherein the metal of said complexes is in the +2 formal oxidation state. More particularly, this invention relates to such complexes wherein the metal is covalently bonded to the cyclic group via the delocalized .pi.-system and also covalently bonded thereto via a divalent ligand group. Such complexes are referred to in the art as "constrained geometry" complexes. The invention further relates to techniques for preparing such complexes, to derivatives of such complexes that are catalysts useful for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers, as well as such polymerization processes.
The preparation and characterization of certain biscyclopentadienyl zirconium and hafnium diene complexes are described in the following references: Yasuda, et al., Organometallics, 1, 388 (1982), (Yasuda I); Yasuda, et al. Acc. Chem. Res., 18, 120 (1985), (Yasuda II); Erker, et al., Adv. Organomet. Chem., 24, 1 (1985); and U.S. Pat. No. 5,198,401. The latter reference describes the use of Cp.sub.2 Zr(diene) as an olefin polymerization catalyst in combination with ammonium borate cocatalysts.
The preparation of certain Ti, Zr, and Hf monocyclopentadienyl diene complexes lacking the present bridged ligand structure, was described in Yamamoto et al., Organometallics, 8, 105 (1989) (Yamamoto) and Blenkers, J, et al., Organometallics, 6, 459 (1987). Only the Hf complexes disclosed in the latter reference were described as having utility as catalyst components.
Constrained geometry metal complexes, including titanium complexes, and methods for their preparation are disclosed in U.S. application Ser. No. 545,403, filed Jul. 3, 1990 (EP-A-416,815) pending; U.S. application Ser. No. 547,718, filed Jul. 3, 1990 abandoned (EP-A-468,651); U.S. application Ser. No. 702,475, filed May 20, 1991 abandoned (EP-A-514,828); U.S. application Ser. No. 876,268, filed May 1, 1992, pending (EP-A-520,732) and U.S. application Ser. No. 8,003, filed Jan. 21, 1993 (WO93/19104), now U.S. Pat. No. 5,374,696 as well as U.S. Pat. No. 5,055,438, U.S. Pat. No. 5,057,475, U.S. Pat. No. 5,096,867, U.S. Pat. No. 5,064,802 and U.S. Pat. No. 5,132,380. The teachings of all the foregoing patents, publications and patent applications is hereby incorporated by reference.
Despite the advance in the art brought about by the foregoing constrained geometry complexes, the adaption of such technology to Group 4 metals in the +2 formal oxidation state has previously been unknown.